Composite article



Sept 29, 1953 H. A. Hu'ssEY ET AL 2,653,884

COMPOSITE ARTICLE Filed Nov. 9, 195o F'fom 72 2n/0 Percent? y weiq/zz' ara/Momma?,

Patented Sept. 29, 1953 4(BWTNP'(SITE ARTICLE Herold Al HusseyA Belmont, amil Donald 1D.

Wright, Watertown, Mass.,assignors to The B. F. Goodrich Company, NewYork,` N. Y., a

corporation-of New York Application November 9, 1950, Seria-l No.194,"838

f A Claims.

AvIt isfa'n objee't'oi this :invention Lto `provide an 'dhesive composition` which isV th'errnosetting, permitting" an article bon-ded: therewith to 'be heated to moderately elevated temperatures Without destroying the adhesive bond.

It is `also anfobjecto this invention to provide a laminated" `article having `anA "adhesive layer therein which has excellent .resistance to sunlight 'deterioration Aand which doesl not discolor upon exposure to sunlightr Another object of 4this invention is to provide mlmethodfeffsecunely :bonding a fexible syn thetic resin; 4:plestfloized polyvinyl i chloride or vinylfichloridewcopolymers, to a :rigid material, 'suchessa metaliconrposition `orwood --tofform an integral unit. y

Still another object of this invention is to provide an adhesive compositimiwhich is easily handled and .non-tacky, when .inra dry condition.

It is 'also an object of this invention to provide an' adhesive composition which may be employed in the' `form 'of 'a-solution invavo'latilesolvent;

Still fanother object of -this-"inventionis te pro*- vide an adhesive -composti'on'wliich -inay Joe readeily cured or thermosetffby'heating-'to-apredetermined .temperature but` which `is vstable at lower temperatures, so asito permit storagefforextended periods of time.

r Other objects :of this `inventior-i will befor)parent from the drawingnnd description which follow.

The Vheretofore mentioned-objectives are `attained by preparing nn'adhesi've composition com.- prising a homogeneous blend of a rubbery butauzu-'enenerylonitrile copolymer and a 'vinyl chloride- 'vllyl'idene chloride copolymer. vSuitable vullaccelerating, reinforcing ingredients, and llers may be incorporated with therefore'- mentioned copolymerswtonfomn a solid adhesive composition which may be utilized in the form of llnlelhfolcedhe'etr may 'be d'issolvdor disperfetti: in an appropriateliquid medium to form na; cement. An excellent bond is obtained between two rigi-dmembers, such as metal or wood members, orbetween a'ri'gld member and arubbery flexible membergsueh. ausja member formed et a .plesticized polyvinylchloride copolymer; or ibetween two rubber-y flexible members .by .interpos- 'ing an :adhesive ineltiiielcomprising our adhesive composition between the members to bef-bonded and then subjecting the `compositel assemblyA lto heat and pressure torvulcanize the adhesive-com- "position,` thereby forming; the assembly into an integral unit. v

The lrawihgls a View 'in Sdtin oi-2a laminated article embodying this invention.

shown 'inthe drawing, Vthe article includes e 'laminated structure comprising a rigid Abase 2` member I l, for example wood or a metal suchzas steellorialuminumy and yazleyer of exible'thermo plastic vfrx'lateriatl Mobonded thereto by means intervening layers `lli-eind v'I3 of adhesive:compo.` sition.

Surface Imember I4 prefere-bly comprises a -preforrned' layer for! :al plasti'eized polymer 'ofa monomeric material :comprising predominantly a onloroeethylenef containing from Ione `to two -chorine atoms on one only-oi the'ea'rbon atoms. Among: .su-ch-A materialsl are V.polymers ofi.' vinyl 'chlorideaor vinylidene chloride :or copolymers of these i materielle` with each other-er -with .lesser amountsfof other".copolymerizaible--materialsnontaining axsingle zolenic: double bond -such asfvinyl bromide, vinyl Vfluoride; -vinyl aeetate; vinyl i propionate; vinyl ibutyrate; `vinylidene fluoride; o'iny'lritiene.Y chloroctinoride,J dimethyl ma-lente, "diethyl .chloroi-maleate, dimethyl fumante-.methyl lacrylate, etlmltacrylate, l methyl ."methacrylate, methyl alphasohloroacryl'ate, .fethyleneg isobntylene and the: hire;A -Qf these:` polymers, high molecular Weight*polyviiwltchlorideis, particularly: useful.

ofthe: :usual a ompoundng ingredients` comi.- monly employed in the plastics industry mayalso 'beupresentrinthe surface layer-,5 isuch as pigments, fillers,,reinforcing agents, plasticizers,stabilizers, f'tca Adhesive layer :I3 in Contact withsmface mem =ber *M vcompriseseslaf .mixture -ofz a rubbery;A butefdiene-acrylonitrile :copolymer ywith Y -acopolymer of; vin-yl f chloride landi vinylidene chloride,- o while adhesive layer I2 in Contact withrbaxselmemberfflil `ooimzirises :a mixture yof the same `A.two ingredients :together withfe polymerv obtainedrby-polymerize `.ingtogether from im `:to 95: per -cent by weight-hof `vinyl chloni'de,- from 4 130:25 `per nent by `Weight 'of vinylabetateandffrom 'l/; tez-1,0` .-percen't by vWeight of e ,-monomerwselected `from the class-:consisting vof alpha-beta i unsaturated,dicarboxylic Aa'cidsrafnd alphafbeta unsaturated `dicarboxylic acidlanhydrides n Allhe rubbery, Vulcanizable butadiene-:acrylamivtrilellcopolyrner component offour adhesive come position comprises asrnbbery, copolymer obtained bythe polymerization or an openechainlaliphatic conjugated diene. containingiromofonr to eight carbon atoms, ,exemplified by butadiene-1,3; 1,4- diir'ietliylljltadiene-lg 'ZJSLdimethylQbutadienef- 1,3, and the 1ike,`with acrylonitrile.. The polymerization oi. the open-chain aliphatic. eonu.- 'gat'e"d"-diene with acrylonitle is carried" o u'tjin tlreusual manner using a suitable catalytic agent, Y

suoli' 'as-potassium persulfate, to imtate*thereL action; Preferahiy theV ru'bbery butadiene:- acrylonitrile copolymer componenitpffour adhesivel'composition has "a combined acrylonitrile from 80 to 100 points when tested according toA the procedure described in A. S. T. M. Standards on Rubber Products under specification Dy -41, a, minimum tensile strength of 3700 pounds per square inch at 77 F., a minimum ultimate elongation at 77 F. of 550 per cent, and a volume swell of from 12 to 20 per cent when tested according to the procedure described in Method A, of specication D 371-46'1 of the A. S. T. M. Standards on Rubber Products. Appropriate llers, softeners, Vulcanizing agents, accelerators, etc. may be `incorporated into the butadiene-acrylonitrile copolymer to modify its physical properties.

v mer component of our adhesive composition comprises a copolymer obtained by the polymerization of vinyl chloride with vinylidene chloride Which polymerization is carried out in an aqueous dispersion in the usual manner using a suitable catalytic agent, such as benzoyl peroxide, to initiate the reaction. Preferably the vinyl chloride-vinylidene chloride copolymer has a. combined vinylidene chloride content from 1 to 40 per cent by weight. Most satisfactory results are obtained with a vinyl chloride-vinylidene chlo-l ride copolymer which has a combined vinylidene chloride content from 2 to 5 per cent by Weight. Fillers, modifiers, stabilizers, plasticizers, etc. conventionally incorporated in vinyl chloridevinylidene chloride copolymer compositions may be included in the Vinyl chloride-vinylidene chloride copolymer component of our adhesive composition.

To impart optimum adhesive properties to our adhesive composition, it is preferable that the composition of layer I3 should contain from 40 to 80 per cent by Weight of butadiene-acrylonitrile copolymer based on the total Weight of the butadiene-acrylonitrile copolymer and the vinyl chloride-vinylidene chloride copolymer in the adhesive composition.

A vinyl chloride-vinyl acetate-maleic acid tripolymer is preferably included in the adhesive composition of layer I2 Which is in direct adherent contact with the structural metal or Wood member Il. Preferably the vinyl chloride-vinyl acetate-maleic acid tripolymer in our adhesive composition comprises from 50 to 95 per cent by weight of the total `weight of vinyl chloride-vinyl acetate-maleic acid tripolymer, butadiene-acrylonitrile copolymer vand vinyl chloride-vinylidene chloride copolymer presentin the adhesive composition and has a combined vinyl chloride content of from 70 toV 95 per cent by weight, a

combined vinyl acetate content of from 4 to 25 Vper cent by Weight, and a combined maleic acid rnormally employed in compounding rubbery compositions, such as by milling the ingredients together on a roll mill or by mixing the ingredients in an internal mixer.

Our adhesive composition is particularly adapted to bonding together a rigid structuralmetal member having a relatively high ultimate strength, such as members fabricated from aluminum, steel, stainless steel, brass and copper, and a flexible synthetic rubbery resin member, such as members formed of a plasticized polyvinyl chloride copolymer and the like.

Examples of our adhesive composition embodying this invention are illustrated by the following recipes, however, it will be understood that we do not intend to limit the scope of this invention by the following recipes:

Example I Parts by Material Weight Rubbery butadiene-acrylonitrile copolymer by 150.0

Weight combined acrylonitrile content).

Vinyl chloride-vinylidene chloride copolymer (4% by A50. 0

weight combined vinylidene chloride content) l Dioctyl phthalate 20. 0

Resinous polyester plasticizer (such as Paraplex G- 10.0

which is comprised mainly of a polyester of adipic acid with a small amount of propylene glycol l, 2 and in manufactured by the Resinous Products dz Chemical Company).

Barium stabilizer (such as Staflex QMXA which is com- 6.0

prised mainly of a barium ricinoleate glyceride and is manufactured by Deecy Products Company).

Sulfur 1.0

Benzothiazyl disulfide 1.0

Total 238.0

The butadiene-acrylonitrile copolymer and vinyl chloride-vinylidene chloride copolymer were blended together on a roll'mill and the other ingredients Were compounded intothe copolymer blend in the usual manner.

Example II Parts by Material Weight .Rubbery butadiene-acrylonitrile copolymer (18% by 80.0

weight combined acrylonltrile content). Vinyl chloride-vinylidene chloride copolymer (20% by 120.0 Weight combined vinylidene chloride content). `Resinous polyester plasticizer (such as Paraplex G-40 10.0

- which is comprised mainly of a polyester of adipic acid with a small amount of propylene glycol l, 2 and is manufactured by the Resinous Products a Chemical Company). Barium stabilizer (such as Staflex QMXA which is com- 6.0 prised mainly of a barium rieinoleate glyceride and is y manufactured by Deecy Products Company).

.Dioctyl phthalate .0 Benzothiazyl disulfide. 1.3 Sulfur 1.2

Total 236.5

The composition was prepared as described ln Example I. Example III Parts by Material Weight Rubbery butadicne-acrylonitrile copolymer (35% by 2.5 Weight combined acrylonitrile content). Vinyl chloride-vinylidene chloride copolymer (4% by 7.5 weight combined vinylidene chloride content). Viyllslloride-vinyl I acetate-maleic acid tripolymer 10050 Diocyfpthane f 1.o Resinous polyester plasticizer (such as ParaplexV Cil-40 0.5 which is comprised mainly oi a polyester of adipic acid with a small amount of propylene glycol l, 2 and is manufactured by the Resinous Products & Chemical Company). Bariun stabilizer (such as Stafiex QMXA which is com- 0.3

prised mainly of a barium ricinoleate glyceride and is manufactured by Deecy Products Company). Y Sulfur 0.1 Benzothiazyl disulfide 0.1

'rom 11210 Thecompositionawas preparedfasidescribedin Example Iii Y To.` facilitate the; application: of: our adhesive compositionvto; surfacesfzto: be bonded. together, the adhesive rcompositionz-is. preferably. employed im Etires-form ot :a: solution. obtained;v by dissolving orf suspending...y the. adhesive. composition.. in'. a `volatile liquid .mediumesuchsas an appropriate organicisolyenteforeexamplefmethyl; ;ethyl= ketone onth'elikes.. The adhesive'.A soIut-iommay rk'bexape `plied flto the snrfacesgtof :bei abondedfstog'ether; `in as conventional manner; such .za'sfbyf spreading, spraying; dipping; etc'LA Preferably the. solution: comprisesrfronr 51:-to 75 %.,by weight offfour adhesivefcompositiong. i

A .preferredmethod' ot 1 bonding;Y together a rigidlz'metal member, suclrV as-fa.- member fabricated: from; aluminum, steen. stainless. steel, brasse` or copper,` and; z a. .flexible i synthetici .resin member'r such; a; member .comprising .a v:plasticizedr polyvinyl` chloride; copolymer.:` or a. vinyl acetate; resin and theflike, to apply a. layer of? our 'adhesive compositions. such L asdescribed i11l:xamplez` I or .Y Example: Il'..to` theaface 'ofz the synthetic resin member. to be*` bonded and. a layerA 01E` our adhesive; materiall compri-sing-V a vinyl chloridevinylf acetateemaleic acicl, r tripolymerlsucht as described; rriExample Ill'to the faceofthe: metal. member :to be. bonded; If a solventar.` diluentuis Vincorporated.with thefadhesive materials,.:` the solvent` or4 diluent: is 1 allbwedl to; evaporatebfromi the. adhesive coatings. The coated surfaces of.` themembers-to `be bonded :arezfbroughttogether and the assembly is subjected to heat fand pressure, such as by heatj thcmetal member and thesynthetic resin member may equal 75 pounds per inch width; generally the. synthetic resin surface member fails prior tothe separation of the bond."

The`W surface member may be, given any desired finish by employing a suitable mold 'surface during the bonding step. Laminated structures consisting ofifiiexible synthetic. resin members and rigid members which have a relativelyghigh ultimatefstrength bonded together with anwadhesive .material withinthe purview of this4 invention maybe fabricated into ,numerous shapes by drawing, spinning; embossing'etc.

. lllaimirrated?- articles, in: which. our; adhesive composition isutilizedhave :excellentresistance to .sunlight being. capable of.: withstanding.` sunlight for prolonged periods of time without subsequent deterioration of the adhesive bond or discoloration.

An adhesive composition within the purview of this invention is relatively stable permitting the composition to be stored for long periods of time without serious deterioration occurring.

It is clear that obvious modifications and variations of this invention may be made without departing from the spirit and scope of this invention as defined in the appended claims.

We claim:

1. A composite structure comprising a rigid structural-metal member, a flexible member opposing said structular-metal member in a generally face-to-face relationship, said flexible member comprising a plasticized polymer of a monomeric material comprising predominantly a chloroethylene containing from one to two chlorine atoms on one only of the carbon atoms,

a: :flexiblezresilient adhesive flayerrinterposedrzbe@ tween.; said` structural.-metal.V member.: andA said iexiblelmember.. and. in fdirect. z adherent `contact with thev innerfface. of; saidzfflexible member, said adhesive layer,4 comprising a vulcanized rubberyL -butadienefacrylonitrile copolymer;` hav,- ing. a 1 combined.; aerylonitrile .content-.ott from 10' tcp-45 per centfbyweight ian-d fa. =vir1yl` chlorideSA vinylidene chloride-s copolymer; andA a; second flexible,` resilient-n4 adhesives. layer interposed bes tween said'. structuralfmetal: member a' anda" the rst :said- A adhesive layer .and .directa adherent contact with; .theirf opposing ,faces-,said second adhesive'` .layer comprising.; ai, vulcanized. trubbery butadiene-acrylonitrile copolymenhaving accom-- bined `acrylonitrile content on from. 10ftc .45 Yper cent. :byf weight, a vinyl chloride-vinylidene chloe ridercopolymer'. anch a;...polymer :comprising: from 7.0i. to: 95 per n cent :.byweightof .vinyl-'achlorid'e, fromfito 25 per: cent. :by .weightot vinyl--acctate and about 1 .per `cent by weight fofA maleic. acide.

2. A composite structurercomprising arigid structural-metal.. memben. a., flexible. member comprising; plasticized polyvinyl. chloride op.;- posing .said structural-metal.l member in a.. gen1i erally':face-tofacezrelationship, a` exible' resilient vulcanized adhesive: layerfinterposednbeetween said structuralemetalimember and said exible. member 'and` fdirectzadherent ,contact with the inner face offsaid exible member, said n adhesive.: layer4 comprising.V a, vulcanized rubber-y butadieneracrylonitrile. copolymer fhaving a combined acrylonitrile` content of from 10 to 45 per cent. byzweight'andL-avinyl chloride.- vinylidene chloride copolymer: having acombined vinylideneichloride. content ofiA from: l'. to 40 per cent byweighty. and a second."ilexibletre silient vulcanized adhesivelayer.A interposed fbe tween said Astructur'al-metal.v member ands'.. the i firstsaid adhesiveilayeriand in direct adherent contact .withr theiropposing faces,- said. second adhesive layer comprising a` vulcanized rubbery butadiene -acrylonitrile copolymer having a acombined acrylonitrilecontent ot from 10 `toi 45` per cent by weight,. a. vinyl chloride-vinylidene chloride copolymer havingV acombined vinylidene. chloride l-content fof fromA l to `40 per cent byi weight andfapolymer comprising.` front70 toz95 percent by weightofiivinyl/chloride; from 4 to 25 percent byiweightrofvvinyl.acetateiand about 11 per cent by Aweight of 'maleic zacid.;

3. A composite structurelcomprising. av rigid structuralemetal member, a flexible. resilient Arub:-V bery member.Y comprising plasticized` polyvinyl chloride. opposing said structural-'metal member in a generally face-to-face relationship, a ilexible resilient vulcanized adhesive layer interposed between said structural-metal member and said flexible member and in direct adherent contact with the inner face of said flexible member, said adhesive layer comprising a vulcanized rubbery butadiene-acrylonitrile copolymer having a combined acrylonitrile content of about 35 per cent by weight, a Mooney plasticity of from to 100 points, a minimum tensile strength of 3700 pounds per square inch at 77 F., a minimum ultimate elongation of 550 per cent at 77 F. and a volume swell of from 12 to 20 per cent and a vinyl chloride-vinylidene chloride copolymer having a combined vinylidene chloride content of from 2 to 5 per cent by weight, said butadieneacrylonitrile copolymer comprising from 4i) to 80 per cent by weight of the total weight of butadiene-acrylonitrile copolymer and Vinyl chloridevinylidene chloride copolymer in said adhesive composition, and a second flexible resilient vulcanized adhesive layer interposed between said structural-metal member and the first said adhesive layer and in direct adherent contact with Vtheir opposing faces, said second adhesive layer comprising a vulcanized rubbery butadieneacrylonitrile copolymer having a combined acrylonitrile content of from 10 to 45 per cent by weight, a vinyl chloride-vinylidene chloride copolymer having a combined vinylidene chloride content of from 1 to 40 per cent by weight and a polymer comprising from 70 to 95 per cent by weight of vinyl chloride, from 4 to 25 per cent by weight of vinyl acetate and about 1 per cent by Weight of maleie acid.

4. A composite structure comprising a rigid structural-metal member, a flexible member comprising plasticized polyvinyl chloride opposing said structural-metal member in a generally face-to-face relationship, a exible resilient vulcanized adhesive layer interposed between said structuralmetal member and said flexible member and in direct adherent contact with the inner face of said synthetic rubbery resin member, said `adhesive layer comprising a vulcanized rubbery `butadiene-acrylonitrileV copolymer having a combined acrylonitrile content of from 10 to 45 per cent by weight and a vinyl chloride-vinylidene Vchloride copolymer having a combined vinylidene chloride content of from i to y40 per cent by Weight, and a second flexible resilient vulcanized adhesive layer interposed between said structural-metal member and the first said adhesive layer and in direct adherent contact'with their .opposing faces, said second adhesive layer comprising a vulcanized rubbery butadiene-acrylo- 4nitrile copolymer having a combined acrylonitrile Icontent of from v10 to 45 per cent by weight, a

' vinyl chloride-vinylidene chloride copolymer `having a combined vinylidene chloride vcontent of from l to 40 per cent by weight and a tripoly- 'mer comprising from 70 to 95 per cent by weight of vinyl chloride, from 4 to 25 per cent by Weight lof vinyl acetate and from 1/2 to 10 per cent by Weight of a monomer selected from the class consisting of alpha-beta unsaturated dicarboxylic acids and alpha-beta unsaturated dicarboxylic acid anhydrides, said second adhesive layer comprising from 50 to 95 per cent by weight of said tripolymer based on the total weight of said buta- 1` diene-acrylonitrile copolymer, said vinyl chloride-vinylidene chloride copolymer and said tripolymer present in said second adhesive layer and said second adhesive layer comprising from 40 to 80 per cent by weight of said butadiene-acrylo- 8 nitrile copolymer based on the, total weight of said butadiene-acrylonitrile copolymer and said vinyl chloride-vinylidene chloride copolymer `present in said second adhesive layer.

5. A composite structure comprising a rigid structural-metal member,` a flexible member opposing said structural-metal member in a generally face-to-facerelationship, said flexible member comprising a plasticized polymer of monomeric material comprising predominantly a chloroethylene containing from one to two chlorine atoms on one only of the carbon atoms, a exible resilient adhesive layer interposed between said structural-metal member and said ilexible member and in direct adherent contact with the inner face of said ilexible member, said adhesive layer comprising a vulcanized rubbery butadiene-acrylonitrile copolymer and a vinyl chloride-vinylidene chloride copolymer, and a second flexible resilient adhesive layer interposed between said structural-metal member and the rst said adhesive layer and in direct adherent contact with their opposing faces, said second adhesive layer comprising a vulcanized rubbery butadiene-acrylonitrile copolymer, a vinyl chloride-vinylidene chloride copolymer and a polymer comprising from 70 to 95 per cent by weight of vinyl chloride, from 4 to 25 per cent by weight of vinyl acetate and from 1A?. to 10 per cent by weight of a monomer selected from the class consisting of alpha-beta unsaturated dicarboxylic acids and alpha-beta unsaturated dicarboxylic acid anhydrides.

HAROLD A. HUSSEY.

DOYNALD D. WRIGHT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,329,456 Campbell Sept; 14, 1943 2,330,353 Henderson Sept. 28, 1943 2,352,705 Garvey et al July 4, 1944 2,462,029 Perry Feb. 15, 1949 2,476,832 Donia July 19, 1949 2,576,148 Schectman Nov. 27, 1951 FOREIGN PATENTS Number Country Date 569,666l Great Britain June 4, 1945 599,937 Great Britain Mar. 24, 1948 OTHER REFERENCES Vinylite Elastomeric Compounds Plastic Bonding, 16 page booklet published 1944 by Carbide &

Carbond Chem. Corp., N. Y., pages 6, 7, 10-1'4. 

1. A COMPOSITE STRUCTURE COMPRISING A RIGID STRUCTURAL-METAL MEMBER, A FLEXIBLE MEMBER OPPOSING SAID STRUCTURAL-METAL MEMBER IN A GENERALLY FACE-TO-FACE RELATIONSHIP, SAID FLEXIBLE MEMBER COMPRISING A PLASTICIZED POLYMER OF A MONOMERIC MATERIAL COMPRISING PREDOMINANTLY A CHLOROETHYLENE CONTAINING FROM ONE TO TWO CHLORINE ATOMS ON ONE ONLY OF THE CARBON ATOMS, A FLEXIBLE RESILIENT ADHESIVE LAYER INTERPOSED BETWEEN SAID STRUCTURAL-METAL MEMBER AND SAID FLEXIBLE MEMBER AND IN DIRECT ADHERENT CONTACT WITH THE INNER FACE OF SAID FLEXIBLE MEMBER, SAID ADHESIVE LAYER COMPRISING A VULCANIZED RUBBERY BUTADIENE-ACRYLONITRILE COPOLYMER HAVING A COMBINED ACRYLONITRILE CONTENT OF FROM 10 TO 45 PER CENT BY WEIGHT AND A VINYL CHLORIDEVINYLIDENE CHLORIDE COPOLYMER, AND A SECOND FLEXIBLE RESILIENT ADHESIVE LAYER INTERPOSED BETWEEN SAID STRUCTURAL-METAL MEMBER AND THE FIRST SAID ADHESIVE LAYER AND IN DIRECT ADHERENT CONTACT WITH THEIR OPPOSING FACES, SAID SECOND ADHESIVE LAYER COMPRISING A VULCANIZED RUBBERY BUTADIENE-ACRYLONITRILE COPOLYMER HAVING A COMBINED ACRYLONITRILE CONTENT OF FROM 10 TO 45 PER CENT BY WEIGHT, A VINYL CHLORIDE-VINYLIDENE CHLORIDE COPOLYMER AND A POLYMER COMPRISING FROM 70 TO 95 PER CENT BY WEIGHT OF VINYL CHLORIDE, FROM 4 TO 25 PER CENT BY WEIGHT OF VINYL ACETATE AND ABOUT 1 PER CENT BY WEIGHT OF MALEIC ACID. 